The American College of Radiology and the American Brachytherapy Society practice parameter for the performance of radionuclide-based high-dose-rate brachytherapy

Brachytherapy is a radiation therapy method in which radionuclide sources are used to deliver a radiation dose at a distance of up to a few centimeters by surface, intracavitary, intraluminal, or interstitial application. This practice parameter refers only to the use of radionuclides for brachytherapy. Brachytherapy alone or combined with external beam therapy plays an important role in the management and treatment of patients with cancer. High-dose-rate (HDR) brachytherapy uses radionuclides such as iridium-192 at dose rates of 20 cGy per minute (12 Gy per hour) or more to a designated target point or volume. High-dose-rate (HDR) brachytherapy is indicated for treating malignant or benign tumors where the treatment volume or targeted points are defined and accessible.

SU-E-T-10: Monte Carlo Study of the Dose Enhancement Factor (DEF) for Gold Nano-Particle (GNP) on the Cellular Level

PURPOSE

In megavoltage external beam radiotherapy, in vivo cell experiments suggest GNP could be used as a radiosensitizer by having radiation dose enhancement factor (DEF) significantly larger than 1. However, Monte Carlo (MC) simulations published in the literature failed to give prove, in which most of them only simulated the interactions between the radiation beams and a single GNP. In this study, we built a multi-GNPs model considering possible spatial arrangements of GNPs relative to a cell to calculate the DEFs of GNPs.

METHODS

Geant4 MC code with G4DNA physics model which can trace electrons down to eV level was used. Two types of geometry models representing different GNP-cell binding were created with each GNP modeled individually: (1) shell model with GNPs randomly and sparsely distributed in a shell in water mimicking when the GNPs were binding to the cell membrane, and (2) sphere model with GNPs randomly and sparsely distributed in a sphere in water mimicking when GNPs were floating inside the cytoplasm. Photon and electron spectrum at 5 cm in depth in water from a Varian 6MV beam was used as the radiation source. Dose to water inside the shell or the sphere representing cytoplasm were scored and compared to situations without GNPs to calculate the DEF. We also looked into the variation of DEFs due to different GNP sizes and concentrations.

RESULTS

A 35 um water cubic were successfully built in Geant4 with spatial resolution of 100 nm. Preliminary results shown under 200 keV electron irradiation, 100 nm GNPs in the shell model shown increased dose to cell at the beam entrance (DEF = 1.08).

CONCLUSIONS

The computation is undergoing for different GNP sizes and concentrations. Meaningful results are expected on the completion of this study.

SU-E-I-100: Feasibility Study of Gamma-Ray Medical Radiography

PURPOSE

The purpose of this research is to study an alternative technique to conventional x-ray radiography that requires less patient radiation dose, less cost, portable, requires less maintenance, and less power consumption. This research explores the feasibility of using gamma-ray radiography in medical imaging. Gamma-ray medical radiography has the potential to provide alternative diagnostic medical information to X-ray radiography.

METHODS

Approximately one Ci of Am-241 radioactive source which emits monoenergetic 59.5 KeV gamma rays was used in this study. Several factors that influence this feasibility were studied. These were the radiation source uniformity, image uniformity, image quality parameters such as contrast, noise, and spatial resolution. In addition, visual assessment of several human phantom gamma-ray and x-ray images were conducted. The images were recorded on computed radiography image receptors and displayed on a standard monitor.

RESULTS

The radioactive source provided a relatively uniform radiation exposure and uniform images. Image noise was mainly dependent on the exposure time and the source size. Although the contrast depended on the window and level setting, it was also dependent on the exposure time and the source size. Spatial resolution was dependent on the source size and the magnification. The generated gamma-ray images were of lower quality than the X-ray images which was mainly due to the low radioactivity used. However, the gamma-ray images displayed most of the main structures contained in the humanoid phantoms.

CONCLUSIONS

Thisresearch explored the feasibility of using gamma-ray radiography in medical imaging and showed that gamma-ray medical radiography has the potential to provide alternative diagnostic medical information to X-ray radiography. Finally, this research also paves the way for the usage and production of high radioactive Am-241 source that will show high quality medical gamma-ray radiography is feasible.